Trans-1,2-dichloroethylene (t-DCE) is a chlorinated solvent with a boiling point of 48° C. that can be used as a cleaner, e.g., cleaning in a vapor degreaser. In particular, t-DCE has good solubilizing power, especially for fatty substances, such as lubricants, oils, and fats. However, its use has been relatively limited for cleaning purposes because, with a flash point of about 2° C. (36° F.), t-DCE is highly flammable.
Prior methods to provide “non-flammable” t-DCE have focused on mixing it with large quantities of a non-flammable compound having a volatility similar to that of t-DCE. For example, such volatile compounds included hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFC's) and the like. These methods relied upon forming azeotropic blends of t-DCE and other components to suppress (raise) the flash point. Such azeotropic mixtures maintain substantially the same composition in the liquid phase and in the vapor phase at the boiling point of the azeotrope. These azeotropic compositions can behave as single solvent degreasing solutions and, as such, are used as solvents in degreasing metal components and cleaning various surfaces in systems where the solvent may be required to continuously evaporate and condensate without fractionation. However, the use of significant proportions of popular HCFC's and HFC's has become disfavored because of their environmental impact: HCFC's have ozone depletion characteristics and non-flammable HFC's are considered “super greenhouse” gases with high global warming potentials.
Other azeotropes and quasi-azeotropes based upon HFC's and t-DCE have been developed. Unfortunately, many HFC's exhibit combinations of properties which are not optimal for safe cleaning. For example, difluoroethane (HFC-152a) and 1,1,1-trifluoropropene (HFO-1243zf) are both flammable and both exhibit very low boiling points. This property makes these azeotropes preferable in applications such as blowing agents, but they are not viable for use in many cleaning applications. Also, although there are distinct advantages to using such azeotropes and quasi-azeotropes, azeotropes and quasi-azeotropes have limited versatility and usefulness as they represent a naturally occurring, fixed ratio of components, sacrificing desirable properties, such as higher solvency, achieved with other ratios of the components. Azeotrope refers to, e.g., a solution of two or more liquids, the composition of which does not change upon distillation.
A need exists, therefore, for a solvent composition that is nonflammable, with a lower environmental impact (i.e., it does not deplete the ozone), and capable of multiple applications (i.e., versatile), in addition to having strong solvency/cleaning power.